Test probe and connector

ABSTRACT

An improved probe includes a conductive tubular housing or body containing a coil spring and a conductive plunger movable in the housing and having a contact tip outwardly extending from one end of the housing. The plunger and tip are urged to a normally outward position by the bias force of the spring. The opposite end of the housing has an opening for mating with a conductive pin of a connector. The connector is retained in a mounting plate of an associated fixture and has terminal ends of desired configuration. The terminal end may include a wire-wrap pin, a crimp type terminal for attachment to a wire, or the terminal may include a spring loaded pin for engagement with an associated electrical contact. An air tight seal may be provided between the probe and the connector and the connector may be mounted in a mounting such that when vacuum is applied to an associated test fixture, air cannot be drawn through the fixture or through the body of the probe.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of U.S. Provisional ApplicationNo. 60/205,045 titled Socketless Probe and filed May 18, 2000.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] N/A

BACKGROUND OF THE INVENTION

[0003] The present invention relates to probes that are used in printedcircuit board test fixtures and more particularly, to a socketless,leaktight replaceable probe for use in a test fixture.

[0004] It is known to provide testing fixtures for printed circuitsboards (PCBs) and the like, for testing the integrity of the electricalconnectivity of the circuit boards. A conventional embodiment of atesting apparatus is shown in FIG. 1, and includes a fixed, stationarysubstantially horizontal probe plate 10 and an overlying verticallyspaced movable top plate 12. Top plate 12 is linked to probe plate 10 bymeans of a peripheral elastomeric spacer 14 which allows top plate 12 tovertically move towards probe plate 10 upon a vacuum being createdinside the sealed enclosure formed by probe plate 10, spacer 14, topplate 12, and an overlying pressure plate (not shown) sealingly engagingthe upper face of top plate 12. The downward movement of top plate 12 isaccomplished by elastomeric spacer 14 partly collapsing under themovable top plate 12 being sucked downwards by the vacuum.

[0005] Top plate 12 holds on its upper surface a printed circuit board18 which is securely anchored thereto by the above-mentioned pressureplate upon the vacuum being created. Circuit board 18 is spaced from topplate 12 by means of rigid spacers 20, 22 and is aligned, relative toprobe plate 10, by means of a number of alignment rods 16 which arefixedly attached to probe plate 10 and which upwardly extend through andloosely engage respective vertically registering channels 23 provided intop plate 12 to engage alignment holes provided in circuit board 18.

[0006] A number of tapered channels 24 extend transversely through topplate 12, with a test probe 26 being located under and verticallyregistering with each channel 24. Each test probe 26 is fixedly attachedto probe plate 10 in a manner described hereinafter, and verticallyextends above and below probe plate 10. Top plate channels 24 furthervertically register with electrical contact points 28 to be tested onprinted circuit board 18 upon engagement with the probe tip of the testprobe 26. Thus, upon top plate 12 moving downward, the probe tip of thetest probe 26 abuts the selected contact point 28 to be tested on theprinted circuit board 18. Through the instrumentality of known software,electric current is transmitted sequentially through selected probes totest the integrity of the electrical connectivity of the printed circuitboard 18.

[0007] The probes 26 of known construction are removably inserted in asleeve (socket) 30 fixedly anchored to the probe plate 10. Sleeve 30 inturn is connected to a computer-controlled circuit which allowselectrical current to be selectively transmitted therethrough. Probe 26includes a tube in which a plunger is vertically movable under the biasof a spring, between a lower and an upper limit position. The plunger,the tube and the sleeve are all electrically connected to each other,for allowing the electric current to be transmitted to the printedcircuit board. The movable plunger is continuously biased upwardly, andis downwardly forced against the bias of the spring when the printedcircuit board downwardly moves against the upper tips of the probes whenthe vacuum is created inside the sealed enclosure. The purpose ofproviding a probe which is distinct from its holding sleeve is that theprobe has a limited life span, and will thus have to be changed after acertain number of uses because of wear.

[0008] Three important problems exist with the above-describedconventional circuit board testing apparatus:

[0009] a) The first problem is that the stationary sleeves holding theprobes prevent the use of more sturdy probes for any given probespacing. In fact, the contact points of the probes on the printedcircuit boards are closely adjacent to one another, and thus the probesneed to be positioned in a closely adjacent fashion. This is becomingmore and more important as the miniaturization of the printed circuitboards evolves. Thus, if the contact points of the probes on a printedcircuit board are very close to one another, probes of a smallerdiameter need to be used to allow the probes to be positioned closer toeach other. Since the sleeves carrying the probes have a larger diameterthan the probes themselves, circuit board contact points which arecloser to one another require sleeves of smaller diameter, andconsequently probes of even smaller diameter. Probes having a very smalldiameter are less sturdy and more prone to accidental breakage.

[0010] b) The second problem is that the vertical alignment of the probetips with their respective registering circuit board contact points isin practice not always achieved. Indeed, when inserting the probesinside their respective sleeves, a certain vertical angular offset mayoccur. The top plate channels are tapered to promote self-alignment ofthe probes therein; however, the probe tips may still be slightlymisaligned when they protrude beyond their respective channels in thespace between the top plate and the printed circuit board. Theconsequence of this misalignment is that the probe tips may be allowedto contact the printed circuit board in a slightly offset fashionrelative to their intended respective contact points, which may resultin electric current not being transmitted to the circuit board. Thus,the testing software could falsely indicate a connection error.

[0011] c) The third problem also relates to a possible misalignmentbetween the probe tips and their corresponding intended circuit boardcontact points, due to the fact that the alignment rods, which are usedto position the circuit board, are fixed to the probe plate. Indeed, itis possible that a misalignment of the top plate relative to the probeplate may result in the top plate through-channels being laterallyoffset relative to their corresponding underlying probes, since thecircuit board position is determined by the alignment roads which areintegrally attached to the probe plate, while the position of thethrough-channels depends on the position of the top plate. If thethrough-channels are laterally offset relative to their correspondingprobes, then certain probes may be laterally deflected by the edges oftheir corresponding through-channels when the top plate is lowered,which may result in the tips of these deflected probes abutting againstthe circuit board aside from their intended position. Again, the testingsoftware would then detect a connection error on the printed circuitboard where there is none.

[0012] Reference is here also made to U.S. Pat. No. 4,885,533 assignedto the assignee of the present application which discloses a probewhich, in use, is firmly engaged in an electrically conductive socketmounted tightly in a dielectric plate of a PCB testing fixture.

BRIEF SUMMARY OF THE INVENTION

[0013] In accordance with the present invention an improved probe andconnector are disclosed that are adapted for use in a printed circuitboard test fixture. The probe includes a conductive tubular housing orbody and a conductive plunger that is contained and movable within thehousing. The plunger includes a contact tip that extends out one end ofthe housing. The plunger and tip are urged to a normally outwardposition by a bias force created by a coil spring disposed within thehousing. At the opposing end of the probe from the contact tip, theprobe end defines a bore that is suitable sized to receive a cooperativepin located at one end of a connector.

[0014] The connector includes a tubular body that may be mounted in athrough-hole within a fixture plate. The connector may be fixedlyretained within the fixture plate via an annular barb or a plurality ofannular beads located on the tubular body. In a preferred embodiment,the connector includes the connector pin at one end and a terminal of adesired configuration at the opposing end. The terminal may include awire-wrap pin, a crimp type terminal for crimp attachment to a wire, ora spring loaded plunger for wireless conductive engagement with anelectrical contact such as is located on a printed circuit board. Theconnector pin receiving end of the probe may contain one or more detentsfor retaining in the end to retain the probe on the connector once theconnector pin is disposed in assembled relation with the probe bore.

[0015] Additionally, the connector includes a tapered portion betweenthe connector pin and the connector body. The tapered portion increasesin diameter from the connector pin to the connector body so that an airtight seal is created between the probe and the connector upon seatingof the pin receiving end of the probe over the connector pin.

[0016] Other features, aspects and advantages of the presently disclosedprobe and connector will be apparent from the Detailed Description ofthe Invention that follows.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0017] The invention will be more fully understood by reference to thefollowing Detailed Description of the Invention in conjunction with thedrawings, of which:

[0018]FIG. 1 is a schematic side elevation showing a prior art circuitboard testing fixture;

[0019]FIG. 2 is a schematic elevation showing a circuit board testingfixture according to the present invention;

[0020]FIG. 3 is a cross-sectional side elevation of a sleeveless testingprobe according to the present invention;

[0021]FIG. 4 is an under view of the probe of FIG. 3;

[0022]FIG. 5 is an elevation of one embodiment of connector forconnecting and supporting the probe of FIGS. 3;

[0023]FIG. 6 is a sectional elevation of an alternative embodiment tothe connector of FIG. 5;

[0024]FIG. 7 is an illustrative arrangement showing various probe anconnector implementations;

[0025]FIG. 8 is a partial side view of the probe plunger of FIG. 3illustrating alternative embodiments of probe tips that may be employed;

[0026]FIG. 9 is a schematic side elevation illustrating one embodimentof a connector for use with the test probe depicted in FIG. 3; and

[0027]FIG. 10 is a schematic side elevation illustrating anotherembodiment of a connector for use with the test probe depicted in FIG.3.

DETAILED DESCRIPTION OF THE INVENTION

[0028] The entire disclosure of U.S. Provisional Application No.60/205,045 titled Socketless Probe and filed May 18, 2000 is herebyincorporated by reference.

[0029]FIG. 2 depicts a circuit board testing fixture 40 with a probe andone embodiment of probe connector in accordance with the presentinvention. A testing fixture 40 includes a movable dielectric top plate42 provided with a number of bores 44 which transversely extend throughthe top plate 42. These will be detailed hereinafter. Testing fixture 40further comprises a dielectric intermediate alignment plate 46 which isspaced from top plate 42 by a peripheral elastomeric spacer 48 of knownconstruction. A dielectric lower probe plate 52 is located spaced underintermediate plate 46 by a rigid peripheral wall 54. A printed circuitboard 58 to be tested is installed so as to rest on the top surface oftop plate 42 and is properly positioned relative to top plate 42 bymeans of alignment rods 60, 62 which protrude from and are fixed to topplate 42 and which engage holes (not shown) in printed circuit board 58.As known in the art, a pressure plate 64 is positioned spacedly overprinted circuit board 58, plate 64 being supported by a rigid peripheralwall 66 provided with an underlying peripheral elastomeric pad 70.Downwardly projecting fingers 74, 76 are integrally carried by anintermediate portion of pressure plate 64.

[0030] A number of testing probes 78 (only one testing probe being shownin FIG. 2) are provided on testing fixture 40. Referring to FIGS. 3 and4, each testing probe 78 comprises a gold clad electrically conductivehollow tube 80 which is engaged by a vertically slidable gold-platedelectrically conductive plunger 82 continuously upwardly biased by acoil spring 84. Plunger 82 has a gold-plated probe tip 85 and isprovided at its intermediate portion with an annular shoulder 86 whichabuts a complementary upper annular seat 88, adjacent the upper end oftube 80, to prevent plunger 82 from moving beyond an upper limitposition under the bias of spring 84. Between the seat 88 and the openend 89 of the tube 80, through which the plunger 82 extends to the tip85, is a reduced diameter elongate retaining and sliding bearing region90 produced by swaging or rolling the tube 80 radially inwardly againsta reduced diameter outer portion 91 of the plunger 82 connecting theannular shoulder 86 with the tip 85. This bearing region 90 has a closeclearance with the outer portion 91 to provide excellent tolerance toside loading forces and smooth long life reciprocal axial movement ofthe plunger 82 against the bias of the spring 84 with no edges orcorners to contact, scrape and wear the plunger 82. Additionally, theswaging or rolling of the tube 80 against the outer portion 91 of theplunger 82 produces the desired clearance between the bearing region 90and the outer portion 91 as a result of material spring back(hysteresis) following the swaging or rolling operation.

[0031] Tube 80 also has a lower annular spring seat 92 against whichrests the lower end of spring 84. Plunger 82 preferably has an inclinedlower surface 93 which is engaged by the upper end of spring 84, tosimultaneously bias plunger 82 upwardly and radially against tube 80 toensure a reliable electrical connection between plunger 82 and tube 80.The lower end of tube 80 comprises an axial bore 94 for sealed resilientconnection between tube 80 and a connector 96 (see FIG. 5) providinggood electric transmissibility and probe support.

[0032]FIG. 2 show that probe 78 is carried by a connector 96 fixedlyanchored in probe plate 52, and more particularly that connector 96engages bore 94, as will be detailed hereinafter. Moreover, probe 78,and more particularly tube 80, extends through intermediate plate 46 ina registering guiding channel 81 provided therein.

[0033] A sealed enclosure is formed between lower probe plate 52 andpressure plate 64, with channels 81 and 44 providing for fluidcommunication the areas between plates 52, 46, 42 and 64. A vacuum port(not shown) is provided in probe plate 52, to allow a vacuum to becreated in the sealed enclosure.

[0034] In use, a vacuum is created in the sealed enclosure, wherein theelastomeric peripheral spacer 48 will gradually collapse to allow topplate 42 to downwardly move towards intermediate plate 46 for the probetips 85 to come into contact with selected registering contact points onprinted circuit board 58; and wherein the peripheral elastomeric pad 70will also collapse to allow pressure plate 64 to move towards top plate42 whereby the fingers 74, 76 of pressure plate 64 will abut against andfirmly support printed circuit board 58 against the upward bias of thenumerous probe plungers 82.

[0035] The guiding channels 81 provided in intermediate plate 46 willcorrectly vertically align probes 78 SO that they register with thecontact points on circuit board 58 which they are intended to contact.Moreover, the top plate throughbores 44 also promote properself-alignment of probes 78 relative to the corresponding circuit boardcontact points. Indeed, the top plate bores 44 each have a lower portion44 a of increased diameter, which allows the corresponding probe tip 85to engage the bore 44 even if the probe tip is slightly misaligned; atapered intermediate neck portion 44 b, which allows the probe tiporientation to be corrected if it is slightly misaligned; and anelongate upper portion 44 c which extends up to the printed circuitboard 58 and which has a diameter to guide the corresponding probe tip85 to the circuit board contact point.

[0036] Additionally, the fact that circuit board 58 rests directly ontop plate 42 and is positioned thereon by means of the alignment rods60, 62 which are fixedly attached to the top plate 42, ensures that thecontact points of circuit board 58 which are intended to come intocontact with respective probe tips 85, will be properly aligned relativeto the top plate bores 44. Thus, in view of these improvements overprior art devices, misalignment of the probe tips 85 relative to theircorresponding intended circuit board contact points is very unlikely, ifnot almost completely obviated.

[0037] Also, according to the invention, the testing probe 78 is notinstalled in a socket or sleeve, as with prior art devices. Indeed,probe 78 engages a connector 96 directly, through the instrumentality ofits axial bore 94. The intermediate plate guiding channel 81 allowsvertical alignment of the probe to be achieved even though no elongatesupporting socket or sleeve is present.

[0038] The axial bore 94 is an elongate cylindrical bore defined by acylindrical tubular extension 98 of the tube 80 opposite the elongatebearing 90. The tubular extension 98 extends from an annular shoulderforming the spring seat 92 and is coaxial with the longitudinal axis 99of the tube 80, spring 84 and plunger 82. The tubular extension 98defines a circular connector pin receiving opening 100 which is itselfdefined by a smooth circular inner edge 101.

[0039] The tubular extension 98, as with the bearing region 90, isintegral with the remainder of the tube 80 and may be formed by rollingor swaging.

[0040] At least one detent 102 is pressed or stamped inwardly into thewall of the extension 98 intermediate the length of the extension 98between the shoulder for the spring seat 92 and the opening 100.Preferably there are three such detents 102 evenly spaced about thecircumference of the extension and in a plane normal to the axis 99. Thedetents 102 do not perforate the tubular extension 98.

[0041] Alternatively, the one or more detents can be provided in aseparate tube, rather than the extension of the main tube.

[0042] Referring now to FIG. 5, a first embodiment of connector 96 isdescribed. The connector 96 is gold plated, electrically conductive andincludes a connector pin 103 terminating in an annular curved tip, tofacilitate entry into probe bore 94 (FIG. 3) through opening 100 and aparallel portion 104 to closely fit within the probe bore 94 and toengage the detent(s) 102 to resiliently and firmly, but removably,support and retain the probe 78 on the connector 96 in good electricalcontact therewith.

[0043] The inner end of pin 103 remote from the curved tip terminateswith an annular taper 105 sized to sealingly engage the smooth circularedge 101 of the probe extension opening 100 when the connector pin 103is fully engaged in the bore 94.

[0044] The connector pin 103 is connected to a wire-wrap pin 109 by wayof a plate connector portion 106 sized to extend through plate 52 (FIG.2) and to be fixedly mounted in a circular opening extending through theplate 52. The fixed mounting is, as shown, by an interference fit aidedby an annular plate engaging ridge 107. Alternative fixed mountingscould be provided by splines on the portion 106, the use of adhesives,molding-in, etc., as would be well known to those skilled in thistechnology.

[0045] A positive stop flange 108 is designed to control the degree ofinsertion of the connector 96 into the plate 52.

[0046] Typically, by way of example, for a probe having an O.D. of 0.054inch, the bore 94 has an I.D. of 0.0265 inch and the pin 103 has aparallel portion 104 with an O.D. of 0.025±0.0003 inch, a taper 105increasing from the parallel portion 104 to a maximum O.D. of0.028±0.001 inch with an included angle of 15±2 degrees. Probes of thesedimensions with sleeve mounting would require probe spacing in a fixtureof 0.100 inch, whereas with the present invention a center spacing forthe probes without sleeves may be reduced to 0.075 inch. Similarly,center to center reductions apply also to probes of other sizes.

[0047]FIG. 6 illustrates a second embodiment of connector 97. In thisembodiment features common with those of the first embodiment ofconnector will not be described again. The connector 97 is a two-partassembly for connecting an insulated wire 110 to the probe 78 by way ofa gold plated electrically conducting pin 111 externally similar to pin103 but hollow to receive the electrical conductor 112 of the wire 110which is crimped at 113 in the hollow interior of the pin 111 to providegood electrical interconnection. A polyester (nylon) sleeve 114 isattached to the pin 111 by an annular protrusion 115 on an extension ofthe pin 111. The sleeve 114 covers the junction of the pin 111 and theinsulation 116 of the wire 110 and provides for the fixed engagement ofthe connector 97 in a circular opening in plate 52.

[0048] The connector(s) 96, 97 are sealingly engaged with the plate 52to provide an air tight mounting such that air and any contaminantscannot be drawn through the fixture or the body of the probe when avacuum is applied during a testing phase.

[0049]FIG. 7 illustrates a variety of probe arrangements providingdiffering probe heights achieved by varying the length of protrudingouter portions 91 of the plungers 82 and/or the axial length of the stopflange 108 of the connectors 96 (or 97). Additionally, this figure showstwo connectors 117, the ends 118 of which include wireless terminationsfor engaging a printed circuit test board. An exemplary connector thatprovides a wireless termination is illustrated in greater detail in FIG.10 and is discussed below.

[0050] The probe 78 may be provided with a probe tip of configurationsthat differ from the probe tip 85 depicted in FIG. 3. Referring to FIG.8, exemplary alternative probe tips are shown. For example, a sphericalprobe tip 130, a spear probe tip 132 or a chisel probe tipe 134 may beprovided on the end of the plunger 91 intended to contact the printedcircuit board 58. Probe tips of other configurations may also be used.

[0051] Referring to FIG. 9 an alternative embodiment of a connector 140having a wirewrap pin termination is depicted installed in the lowerprobe plate 52. The connector 140 includes a connector pin 142, a plateconnector portion 144 and an annular tapered portion 146 between theconnector pin 142 and the plate connector portion 144. Additionally, theconnector 140 includes a wire wrap pin 148 at the opposite end of theplate connector portion 144 from the connector pin 142. Two annularbeads 150 are provided on the plate connector portion 144. The diameterof the annular beads 150 is specified to provide an interference fitwith the respective hole in the lower probe plate 52. Upon insertion ofthe connector 140 within the respective hole in the probe plate 52, theannular beads 150 secure the connector within the probe plate 52 andmaintain vertical alignment of the connector 140 within the probe plate52.

[0052] Referring to FIG. 10 a further embodiment of a connector 160 thatprovides a wireless termination is depicted both with a printed circuitboard 162 present beneath the connector 160 and absent beneath theconnector 160. The connector 160, in one embodiment, is fabricated infirst and second connector portions 164 and 166 respectively. The firstportion 164 includes a connector pin 168 for insertion within the axialbore 94 of the testing probe 78 (FIG. 3). Additionally, the firstportion includes a body 170 and the connector pin 168 extends from oneend of the body 170. A tapered annulus is provided between the connectorpin 168 and the body 170 to provide a seal when the connector pin 168 isdisposed within the axial bore 94 as discussed hereinabove. An axialbore 174 is provided in the end of the first portion 164 opposite theconnector pin 168 to receive a cooperative mating pin 176 at one end ofthe second portion 166 of the connector 160. The mating pin 176 extendsfrom one end of a tube 178. A probe 180 having a probe tip 182 isdisposed within the tube 178 and is urged outward via a coiled biasspring (not shown). As shown in the connector 160 on the left in FIG.10, the probe is disposed in an extended position the absence of theprinted circuit board. As shown in the connector 160 on the right ofFIG. 10, the probe tip 182 is urged into contact with the printedcircuit board 162 so as to make an electrical connection with a contactpoint located on the printed circuit board 162. The first connectorportion 164 includes two annular beads 184 for securing the firstconnector portion 164 within the lower probe plate 52 and maintainingvertical alignment of the connector 160 within the probe plate 52.

[0053] While the connector 160 is illustrated as being fabricated infirst and second portions 164 and 166, in an alternative embodiment, aconnector that permits wireless termination may be fabricated as acomponent that includes a tubular body portion having a connector pin atone end that is sized for insertion within the axial bore 94 of thetesting probe 78. A probe is disposed within the tubular body andincludes a probe tip that extends from the end of the body opposite theconnector pin. A plurality of annular beads may be provided on the bodyto secure the connector within the lower probe plate 52. In this manner,the electrical connection between the mating pin 176 and the bore 174 ofthe first connector portion 164 depicted in FIG. 10 is eliminated.

[0054] An advantage of the presently described probe and connector isthat no sleeves or sockets are used for holding and vertically aligningthe probes. Indeed, the probes are positioned on their correspondingconnectors which engage detents in the probe that resiliently andreleasably hold and support the probe. This prevents the probes frombeing accidentally released e.g. during assembly of the fixture.Moreover, the intermediate plate allows the probes to be substantiallyvertically aligned. The absence of the probe-carrying sockets or sleevesallow the use of probes of larger diameters, for a given required probespacing, which will consequently be more sturdy and less likely to beaccidentally damaged and which will resist wear longer than probes usingsleeves or sockets.

[0055] Also, the alignment of the probes with their respective contacttips on the printed circuit board is enhanced by the presence of the topplate throughbores which extend from the probe tip up to the printedcircuit board, thus preventing the probe tip from being laterally offsetand to contact the printed circuit board elsewhere than on its intendedcontact point thereon. The intermediate plate throughbores, and the factthat the alignment rods are fixed to the top plate instead of the probeplate, also help improve alignment of the probes with their respectiveintended contact points on the printed circuit board.

[0056] It should be noted that the presently disclosed test probes andconnectors may be fabricated of any suitable metal such as beryliumcopper and may be plated with gold or other suitable material to enhanceconductivity and/or to reduce corrosion.

[0057] It will be appreciated by those of ordinary skill in the art thatmodifications to and variations of the above described socketless probemay be made without departing from the inventive concepts describedherein. Accordingly, the invention should not be viewed as limitedexcept as by the scope and spirit of the appended claims.

What is claimed is:
 1. A probe, suitable for use in a socketless fixtureand for providing electrical contact with electrical circuits duringtesting thereof, said probe comprising: an electrically conductivetubular housing; a circuit contacting electrically conductive plungercaptively disposed in said electrically conductive tubular housing inelectrically conductive contact therewith, said plunger having a circuitcontacting tip urged outward from the housing under the force of alongitudinally compressed coil spring; said tubular housing having afirst end portion through which the plunger extends to the tip and bywhich the plunger is retained in the housing and a second end definingan opening sized to receive and retain an electrically conductiveconnector pin forming part of a connector to provide electricallyconductive connection to the probe.
 2. The probe of claim 1, wherein theopening is defined by a cylindrical wall portion of the housing, saidcylindrical wall portion having at least one detent extending radiallyinward of the wall into the opening for resiliently retaining theconnector pin within said opening.
 3. The probe of claim 2, wherein saidcylindrical wall portion includes three circumferentially spaced detentsextending radially inward of the wall.
 4. The probe of claim 2, whereinsaid cylindrical wall portion is of a smaller internal diameter than theinternal diameter of an adjacent portion of the housing so as to providean abutment for the spring.
 5. A probe and connector assembly for use ina socketless fixture and for providing electrical contact withelectrical circuits during testing thereof, said assembly comprising: aprobe comprising: an electrically conductive tubular housing; anelectrically conductive plunger captively disposed in the electricallyconductive tubular housing in electrically conductive contact therewithand having a circuit contacting tip urged outward from the housing underthe force of a longitudinally compressed coil spring; said tubularhousing having a first end portion through which the plunger extends tothe tip and by which the plunger is retained in the housing and a secondend defining an opening; an electrically conductive connectorcomprising: a pin forming part of the connector and sized to achieve aninterference fit with said housing second end when disposed within saidopening, said pin providing electrically conductive connection betweenthe connector and the probe when disposed within said opening.
 6. Theassembly of claim 5, wherein said connector has a pin end and atermination end and said connnector includes a wire wrap terminaladapted for wire-wrap connection to an electrical conductor at saidtermination end.
 7. The assembly of claim 5 wherein said connector has apin end and an opposing termination end, said connector including anelectrically conductive tubular body attached to said pin and anelectrically conductive connector contact plunger disposed in said bodyin electrically conductive contact therewith and having an electricalcontacting connector tip urged outward from said tubular body at saidtermination end of said connector under the force of a longitudinallycompressed connector coil spring to allow wireless conductive contactwith an electrical contact on an adjacent printed circuit board.
 8. Theassembly of claim 5, wherein said connector includes a tubular crimpportion adapted to receive an electrical conductor to permit a crimpcondcutive attachment of said connector to said conductor.
 9. Theassembly of claim 5, wherein the connector has an annular barb formed onthe exterior thereof to provide captive mounting in an opening within afixture plate.
 10. The assembly of claim 5 wherein said connector has acylindrical portion attached to said pin and said cylindrical bodyportion includes two annular externally extending beads for retainingsaid connector via a press fit in an opening within a fixture plate. 11.The assembly of claim 5 wherein said connector includes a taperedportion of increasing diameter extending between said pin and said body,said connector and probe forming a seal when said pin is disposed inassembled relation within said opening defined by said second end withsaid second end in circumpherential abutting relation with said taperedportion of said connector.